A wire coating material should be fire retardant. Thus, compositions comprising fire retardant phenylene oxide polymers showing a high heat resistance have been used therefor. Furthermore, it has been proposed to blend such a phenylene oxide polymer with, for example, polyamide, nylon or polystyrene so as to improve its properties including high-impact strength, fire retardancy and chemical resistance.
Even such an improved phenylene oxide polymer composition as the one described above, however, shows a poor tensile elongation or flexibility. Furthermore, it has a low organic solvent resistance. When it is exposed to a sharp bend or an organic solvent, therefore, cracking might rapidly occur at room temperature. These facts indicate that these conventional phenylene oxide polymer compositions are unsatisfactory as a wire coating materials.
In order to solve the above-mentioned problems, there has been proposed a composition comprising a phenylene oxide polymer, a styrene/olefin/styrene block copolymer and a phosphorus fire retardant. A phosphorus fire retardant is generally in the form of a liquid at room temperature and has a plasticizing effect. Thus, the above-mentioned composition containing the phosphorus fire retardant is excellent in, for example, fire retardancy and mechanical properties. However it has been required to further improve said composition, since it shows serious fuming caused by the phosphorus fire retardant component.
On the other hand, a hydrated metal oxide is known as a fire retardant accompanied by little fuming. However it is required to use a large amount of a hydrated metal oxide in order to achieve a fire retardant effect as high as the one achieved by using the phosphorus fire retardant. As a result, the mechanical properties and low-temperature brittleness of the product are deteriorated.